The effect of cadmium on oogenesis in Xenopus laevis

Reproductive toxicity studies have historically centered on post-fertilizat ion events. A thorough assessment of reproductive hazards to an organism sh ould include all aspects of its life cycle. Cadmium is a teratogenic and ca rcinogenic heavy metal that occurs naturally in the environment but is also released anthropogenically. The effect of cadmium administration on oocyte development in Xenopus laevis was studied. Adult female Xenopus were injec ted in the dorsal lymph sac with cadmium chloride (CdCl2) at doses of 0.5, 0.75, 1.0, 3.0 or 5.0 mg/kg every other day for 21 days. Significant advers e effects of Cd on oocyte development were observed. The percentage of oocy tes at all stages of oogenesis was decreased while the population of atreti c oocytes increased dramatically (P < 0.0001). Numerous oocytes exhibited a speckled or mottled appearance and the incidence of completely atretic ooc yte follicles increased. The observations indicate that Cd has the potentia l to significantly disrupt oogenesis and that examination of developing gam etes may be a useful parameter for assessing the influence of environmental contaminants on reproductive capacity. (C) 2000 Elsevier Science Ltd. All rights reserved.